Garmin MC34676B Manuale Utente

© Freescale Semiconductor, Inc., 2009. All rights reserved.

 

Freescale Semiconductor
User’s Guide

Document Number: KT34676BUG

Rev. 1.0, 2/2009

This User Guide helps the Lithium-Ion (Li-Ion) battery 
charger designer understand the MC34676B and its 
evaluation board. It illustrates the design procedure when 
using the MC34676B to design a Li-Ion battery charger, and 
the way to get the best performance from the MC34676B.

The 34676 is a dual 28V input voltage and fully-integrated 

single cell Li-Ion battery charger, targeting smart handheld 

applications. One of the inputs is optimized for charging with 

a USB port, and the second is optimized for an AC/DC 

adapter power source. The charger has two 28V power 

devices, to eliminate the need of any external power source 

selection and input over-voltage protection circuitry. Each of 

the power devices independently controls the charge 

current from the input, and performs as an independent 

charger. Only one of the two chargers operate at a time.

The AC charger current and the USB charger current are 

programmable, up to 1.2A and 400mA, with an external 

resistor respectively. The voltage across the two external 

resistors is also used to monitor the actual charge current 

through each charger respectively. The EOC current of both 

chargers is the same, and programmable by an external 

resistor. The 4.85V regulator can be used to power a 

sub-system directly.

The 34676 has a 5% constant current accuracy for the AC 

Charger over -40 to 85

o

C, and a 1.0% constant voltage 

accuracy over -40 to 85

o

C. A charge current thermal 

foldback feature, limits the charge current when the IC 

internal temperature rises to a preset threshold.